1. Field of the Invention
The present invention relates to a gate valve mounted on a vacuum chamber in a semiconductor processing apparatus and used for opening and closing an opening communicating with the vacuum chamber and, more specifically to a non-sliding gate valve configured to be capable of opening and closing the opening without sliding.
2. Description of the Related Art
In a semiconductor processing apparatus, a gate valve is used for opening and closing an opening communicating with a vacuum chamber. The gate valve generally includes a valve plate configured to open and close the opening, a valve shaft coupled to the valve plate, and an air cylinder coupled to the valve shaft, and is configured to open and close the opening by bringing a valve seal of the valve plate toward and away from a valve seat surface around the opening by operating the valve shaft with the air cylinder.
Examples of the gate valves include a system for opening and closing a valve plate by causing the valve shaft to tilt about a point as a pivot point and a system for opening and closing the valve plate by moving the valve shaft and the valve plate vertically with respect to the valve seat surface.
From these systems, in the gate valve of the system of opening and closing the valve plate by tilting the valve shaft, since the valve seal receives a predetermined pressing force after coming into contact with the valve seat surface, if the tilting movement of the valve shaft is continued, the valve plate is displaced with respect to the valve seat surface in the direction along the seat surface. Consequently, friction may be generated between the valve seal and the valve seat surface, or the valve seal may rotate within a mounting groove, whereby abrasion powder is generated which may be detrimental to cleaning of the valve.
In contrast, in the gate valve of the system for opening and closing the valve plate by moving the valve shaft and the valve plate vertically with respect to the valve seat surface, since no friction is generated between the valve seal and the valve seat surface, there is no fear of generation of the abrasion powder. Patent Document, Japanese Unexamined Patent Application Publication No. 11-351419, described below discloses a non-sliding gate valve in which no friction is generated between the valve seal and the valve seat surface. This gate valve includes a plurality of links, cam followers and guide grooves interposed between a drive rod (propelling shaft) of the air cylinder and the valve shaft (valve rod), and is configured to close the opening by moving the valve plate from an open position to a position facing the opening in parallel with respect to the valve seat surface around the opening, and then moving the valve plate vertically with respect to the valve seat surface.